This invention relates to a device for reading out information represented by a charge latent image formed on a recording medium.
In some information recording and reproducing systems, information is recorded into a recording medium by forming a charge latent image on the recording medium in accordance with the information. The recorded information is reproduced by detecting the charge latent image on the recording medium.
Some charge latent image detecting devices used in such information recording and reproducing systems include a photo-modulation member which is opposed to a recording medium to undergo an electric field dependent upon a charge latent image on the recording medium. During an information reproducing process, light is applied to the photo-modulation member. The applied light is modulated by the photo-modulation member in accordance with the electric field so that the modulated light represents the charge latent image. The modulated light is converted into a corresponding electric signal representing the charge latent image.
A photo-modulation member using a single crystal of lithium niobate has a problem in sensitivity.
In the case of a photo-modulation member using a twisted nematic liquid crystal cell, thick support glass plates are generally required by the cell so that a sensing part of the cell tends to be distant from a recording medium and is thus liable to undergo a weak electric field.